Propagation of electromagnetic waves through a turbulent atmosphere

Abstract

This review covers the major advances achieved in the studies of EM wave propagation in turbulent media for the last two decades with the focus on new physical problems, effects and formalisms., The greatest attention has been directed to the problem of strong fluctuations of intensity. The theoretical results of this treatise include the path integration technique, the predominant correlation method, the two-scale method, the phase approximation in Huygens' method, the hybrid approach to scattering from small inhomogeneities in the presence of large ones, the theory of coherent channels in backscattering, and the concept of partially determinate processes and fields.New physical effects described in the review include the rise of the coherence radius in intermittent turbulence, backscatter enhancement, doubling the variance of phase, incidence angles, group delay, and frequency shifts in the double passage of waves through turbulent media, the residual scintillation effect, the long correlation effect in backscattering, the partial reversal of wavefronts in turbulent media, the magic cap effect in reflection from phase conjugated mirrors, the strong localization of UHF radic waves in stochastic tropospheric waveguides, the effect of penetration in caustic shadow%, and enhanced translucence. New fields of experimental research have been outlined, such as scattering from vegetation and snow covers, and coherent structures in tuibulences, and new objects of theoretical analysis have been elicited: random dislocations of wsvefronts, fractal^ and critical wave phenomena, and the predictability of random fields.

Long-Range Correlations in the Speckle Patterns of Directed Waves

“…We shall demonstrate the method for the case ℓ tr ≫ Z ≫ ℓ by calculating the speckle correlations and their sensitivity to various perturbations, such as a change in the frequency of the wave, its incidence angle and a change of the refraction coefficient. In many aspects, our results differ from those obtained in the previous studies [4,5,6,7]. Among the differences are the slow power law decay of the density correlator as a function of coor-…”

“…[1,2,3]. The limit of "directed waves" ℓ tr ≫ Z ≫ ℓ has been studied in many papers, see for example [4,5,6,7] and references therein. In the latter case the wave experiences many small angle scattering events, but the total change of its propagation angle θ remains small.…”

“…Thus, conductance fluctuations are not described by Eqs. (3)(4)(5)(6)(7)(8)(9)(10)(11), and should be calculated from the diagrams of the type shown in Fig. 2 f) (see the corresponding discussion in Ref.…”

“…[4,5,6,7]). First, the correlation function (13) exhibits a universal long range power law behavior in a wide range of values of ρ.…”

“…In contrast, in the results presented in Refs. [4,5,6,7] C(ρ) depends on the detailed form of g(r), and usually decays exponentially at ρ > ξ. Second, in contrast with previous results, C(ρ) changes its sign as a function of ρ, which is a consequence of the current conservation.…”